The health benefits of exercise have attracted substantial attention, because regular exercise can strengthen muscles and improve endurance. Physical activity is an integral part of an overall healthy lifestyle, which helps protect against chronic diseases, such as obesity, insulin resistance and type 2 diabetes. In consideration of the differences in duration, intensity, and type of activity of exercise, it is likely to involve different signaling pathways and bring different benefits in different tissues. Here we review our growing knowledge of exercise training adaptations and regulation in cellular processes related to energy metabolism, aging and autophagy, and many important findings remain to be discovered.
Decreased oxygen availability in sojourners requires adjustments in tissue oxygen supply, the most effective of which is an increase in the hemoglobin (Hb) concentration. It is achieved by two independent processes: a fast increase in Hb is achieved by decreasing plasma volume due to enhanced renal Na- and water excretion. A further but slow increase in Hb concentration is achieved by stimulation of erythropoiesis by mechanisms depending on stabilization of hypoxia-inducible factor 2α resulting in elevated levels of erythropoietin in blood. The magnitude of decrease in plasma volume and of stimulation of erythropoiesis depends on the degree and duration of exposure to hypoxia at high altitude. Upon descent from high to low altitude elevated O2-transport capacity is no longer needed. Thus, plasma volume can be restored and excess erythrocytes can be removed from circulation. This latter process is called erythrolysis. Its effectiveness seems to depend on the altitude to which individuals had been exposed. Whereas most of the excess erythrocytes seem to be removed from circulation within 1–2 weeks after a stay at altitudes > 3500 m, total Hb mass seems to remain elevated for up to 4 weeks when individuals had been exposed to more moderate altitudes, e.g. in the range of 2500 m. These are the altitudes where athletes typically perform altitude training. Thus, it appears that improved performance in the weeks after return from altitude training depends in part on maintaining elevated total Hb mass, which is known to increase aerobic capacity.
Sarcopenia, which is characterized by reduction in muscle mass and strength, contributes to several age-related conditions, including insulin resistance and frailty. Despite the importance of maintaining muscle mass for healthy aging, the mechanisms contributing to sarcopenia are not fully elucidated. Nevertheless, mitochondria appear to play a key role in the underlying condition, and importantly, respond robustly to exercise interventions. Mitochondria are intracellular organelles largely attributed to maintaining ATP concentrations, however, the importance of this organelle in overall cellular homeostasis has been expanded in the last decades to include redox signaling, calcium homeostasis, inflammation, and apoptosis. Several lines of evidence suggest that mitochondrial bioenergetics are altered in aged skeletal muscle, resulting in an increase in reactive oxygen species (ROS) production, while conversely genetic/pharmacological approaches that attenuate mitochondrial ROS promote healthy aging and maintenance of muscle mass. These observations suggest that increased free radicals are one of the bases of the aging process and related sarcopenia. Here, we reviewed the current knowledge regarding mitochondrial function and redox balance in aged human skeletal muscle, highlighting the implications of redox unbalance on skeletal muscle mass maintenance and muscle health. Additionally, we describe the benefits of exercise and nutrition interventions in the context of improving mitochondrial bioenergetics and functional outcomes regarding skeletal muscle mass and function.
Low-intensity resistance training (LI-RT) combined with blood flow restriction (BFR) is an alternative to traditional moderate–high-intensity resistance training to increase strength and muscle mass. However, the evidence about the efficacy of this novel training method to increase strength and muscle mass in healthy and older adults with pathologies is limited. Furthermore, the possible risk and adverse effects with BFR training methodology in older adults should be considered.
(1) To summarize the current evidence on training with BFR strategies in older adults aiming to improve strength and to increase muscle mass; and (2) to provide recommendations for resistance and aerobic training with BFR in older adults based on the studies reviewed.
Studies that investigated the chronic responses to resistance training or aerobic training with BFR related to strength and muscle mass changes in older adults were identified. Two independent researchers conducted the search in PubMed, Web of Science, and Google Scholar databases from their inception up to November 1, 2018.
Seventeen out of 35 studies, which performed resistance or aerobic training with BFR in older adults focused on strength and muscle mass outcomes, were included in this review. Studies performing resistance and aerobic training with BFR found better improvements in strength and higher increase in muscle mass compared to non-BFR groups that performed the same training protocol. High-intensity resistance training (HI-RT) without BFR provided greater improvements in strength and a similar increase in muscle mass compared to light-intensity resistance training (LI-RT) with BFR.
Current evidence suggests that LI-RT and/or aerobic training with BFR improves strength and increases muscle mass in older people. Light-intensity training without BFR would normally not obtain such benefits. Therefore, LI-RT and aerobic training with BFR is an alternative to traditional methods to improve strength and by way of an increase in muscle mass, which are important in the elderly who have progressive muscle atrophy and are at higher risk of falls.
Advances in spinal cord injury-based research in the last 50 years have resulted in significant improvements to therapy options. However, the efficacy of such research could be further enhanced if threats to internal and external validity were addressed. To provide perspective, a sample topic was identified: the effects of acute and chronic exercise on clinical and sub-clinical markers of cardiovascular health. The intention was not a systematic review, nor a critique of exercise-based research, but rather a means to generate further discussion. Thirty-one articles were identified, and four common issues were found relating to: (1) sampling; (2) study design; (3) control group; and (4) clinical inference. These concerns were largely attributed to insufficient resources, and challenges associated with recruiting individuals with spinal cord injury. Overcoming these challenges will be difficult, but some opportunities include: (1) implementing multi-center trials; (2) sampling from subject groups appropriate to the research question; (3) including an appropriate control group; and (4) clearly defining clinical inference. These opportunities are not always feasible, and some easier to implement than others. However, addressing these concerns may assist in progressing spinal cord injury-based research, thereby helping to ensure steady advancement of therapy options for persons with spinal cord injury.
The purpose of this study was to determine if lower extremity joint loading was influenced by stride length or shoe midsole cushioning. Ten subjects completed 10 trials of overground running at an average speed of 4.43 m/s in each of three conditions: normal running, running with a stride length (SL) reduced by 10% of normal, and running with a cushioned midsole stiffness (i.e., mechanical impact reduction of 13.7–10.9 g). Reaction forces calculated from inverse dynamics were summed with muscle forces estimated from a musculoskeletal model using static optimization to obtain joint contact forces at the hip, knee and ankle joints. Peak components of the contact forces [axial, anterior–posterior, and medial–lateral (ML)] were examined using parametric statistics (α = 0.05). Reducing stride length resulted in significant decreases in absolute peak ankle contact forces in the axial direction (normal: − 14.5 ± 1.5 BW; reduced SL: − 14.0 ± 1.6 BW) and the ML direction (normal: 0.67 ± 0.23 BW; reduced SL: 0.61 ± 0.21 BW). Reducing stride length also reduced the peak absolute axial forces at the knee (normal: − 10.6 ± 1.3 BW; reduced SL: − 9.8 ± 1.2 BW) and the hip (normal: − 7.26 ± 2.24 BW; reduced SL: − 6.75 ± 2.10 BW). The cushioned shoe did not statistically reduce the peak absolute contact forces from the normal stride condition at any of the joints. Post hoc stress analysis suggested that the observed changes in anterior hip force would increase stress more than any of the other statistically significant results. Reductions in stride length appear to decrease some joint contact variables but cushioning in the heel region of the shoe does not.
Previous work has demonstrated that acute exercise prior to memory encoding may enhance long-term memory. Similarly, other work demonstrates that acute exercise during the memory consolidation period may also enhance long-term memory function. However, no study has evaluated whether long-term memory is enhanced when an acute bout of exercise occurs during both of these time periods, when compared to just prior to memory encoding. A within-subject randomized controlled intervention was employed. On separate laboratory visits, participants completed two main protocols, including (1) exercise before memory encoding and (2) exercise before and after memory encoding. Long-term memory was assessed, via a word-list task, from a 20-min delay period and a 24-h delay period. We observed a significant main effect for time, F(8, 176) = 529.5, P < 0.001, η p 2 = 0.96, but no significant main effect for condition, F(1, 22) = 0.08, P = 0.77, η p 2 = 0.004, or time by condition interaction, F(8, 176) = 0.19, P = 0.99, η p 2 = 0.009. In conclusion, there was no difference in long-term memory function when comparing acute exercise only prior to memory encoding vs. acute exercise both before and immediately after memory encoding.
Few successful strategies address lifestyle and behavior change towards food and exercise among underserved children. Children spend the majority of their day in a school setting, providing an optimal environment to target behavior change with limited resources.
This school-based pilot study was a collaborative effort among professionals from a state university, a county department of health, a county school system, and a nearby regional public hospital to improve knowledge, intentions, and self-efficacy about nutrition and physical activity among underserved children.
Thirty-three, fifth grade students were recruited from a low socioeconomic elementary school (Mean = 10.55 ± 0.56 years). Students were randomly assigned to a treatment (n = 19), or control group (n = 14) for 8 weeks. Once per week, the treatment group received 30 min of nutritional advice, and completed 30 min of functional exercises. Anthropometric and body composition assessments were made, and eating and physical activity behaviors were recorded using the CATCH Kids Club After-School Student Questionnaire at baseline, and at the end of week 8. A 2-way repeated-measure analysis of variance and paired-t tests with Bonferroni adjustments were used to analyze any differences.
Physical activity, intentions, and knowledge for a healthy nutrition behavior increased significantly in the treatment group. However, causal inferences could not be made at this time.
This public sector partnership demonstrated that a simple school-based intervention can play a role in healthy choices among underserved children.
The maximal isometric strength test is widely used in general, athletic, and clinical populations. However, this test has often been used without considering how many trials are needed or appropriate to obtain reliable test scores. Thus, the aim of this study was to examine the maximal isometric strength test in upper and lower body for the purpose of determining the reliability of best isometric strength score and the ideal number of trials for a reliable test score.
One hundred and twelve healthy adults were assigned to four different groups (elbow flexion with the vertical and horizontal forearm positions, knee flexion, and knee extension). After familiarization, all participants performed three maximal isometric voluntary contractions with the designated muscle group. The reliability of best isometric strength test score was calculated using the intraclass correlation coefficients (ICC) from a one-way ANOVA model. The Spearman–Brown prophecy formula was used to identify the minimum number of trials needed.
The reliability of the best maximal isometric strength test scores out of three trials were high (ICC = 0.92 to 0.98). At least two trials of maximal isometric strength test for knee flexion and one trial for elbow flexion and knee extension would be necessary to achieve an acceptable reliability coefficient of 0.80. In addition, one trial of elbow flexion would be enough for women, but men would need two trials.
Our results suggest that overall, at least two trials would be necessary to test isometric strength in upper and lower body muscles in both sexes.